1. Field of the Invention
This invention relates to an image processing method and apparatus for carrying out image processing on digital image signals, which have been acquired with digital cameras.
2. Description of the Prior Art
With digital electronic still cameras (hereinbelow referred to as digital cameras), an image having been acquired with a photographing operation can be stored as a digital image signal on a recording medium, such as an internal memory or an IC card provided in the digital camera. The image having been acquired with the photographing operation can then be reproduced from the stored digital image signal with a printer or a monitor. In cases where the image having been acquired with the digital camera is to be printed, it is desired that an image having image quality as good as the image quality of a photograph printed from negative film can be obtained.
The digital camera is constituted of elements, such as an optical system (an aperture, a shutter, and a strobe), an imaging system (a CCD image sensor and a signal processing system), a control system (AE, AW, and AF), and a recording-reproducing system (compression-decompression, memory control, and displaying). Factors, which affect the image quality of the reproduced image, among these elements include a color temperature of strobe light, AE control, AW control, a CCD color-separation color filter, the number of picture elements, gradation conversion, and matrix operation processing for obtaining luminance and color difference signals. With the digital camera, these factors are controlled, and a digital image signal is acquired such that a reproduced image having good image quality may be obtained.
With the digital camera, instead of the acquired image being submitted to a photo processing shop, the photographer himself can print the acquired image by using a printer or can reproduce the acquired image on a monitor. Therefore, the user can freely print images by himself. However, in order for a print having satisfactory image quality to be obtained, it is necessary that a visible image is temporarily reproduced from the acquired digital image signal with a printer or a monitor and a correction is made by seeing the reproduced image. Therefore, in cases where a large number of prints are to be formed, considerable time and labor are required, and prints cannot be formed efficiently. Accordingly, it is desired that, as in conventional photographic film, the photographer asks a photo processing shop to form prints from the digital image signal such that printed images having good image quality may be obtained.
However, as described above, the factors affecting the image quality of the images reproduced from digital image signals acquired with digital cameras vary for different kinds of cameras, such as different manufacturers and different device types of the digital cameras. Therefore, in a photo processing shop in which prints are to be formed from digital image signals having been acquired with various different kinds of digital cameras, it is difficult to obtain printed images having uniform good image quality from all of the given digital image signals. For example, the forms of acquisition of digital image signals with digital cameras can be classified into a complementary color type and a primary color type in accordance with the device types of digital cameras. With the primary color type of digital camera, a digital image signal can be obtained such that comparatively bright colors may be reproduced. With the complementary color type of digital camera, the R, G, and B colors are presumed from Y, M, and C, and ordinarily the digital image signal is obtained such that the colors cannot be reproduced brightly as with the primary color type of digital camera. Therefore, in photo processing shops, it is necessary that visible images are temporarily reproduced with a printer or a monitor and a correction is made through trial and error. Thus the prints cannot be formed efficiently.